Solid state lighting devices are used for a number of lighting applications. For example, solid state lighting panels including arrays of solid state light emitting devices have been used as direct illumination sources, for example, in architectural and/or accent lighting. A solid state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs). Inorganic LEDs typically include semiconductor layers forming p-n junctions. Organic LEDs (OLEDs), which include organic light emission layers, are another type of solid state light emitting device. Typically, a solid state light emitting device generates light through the recombination of electronic carriers, i.e. electrons and holes, in a light emitting layer or region.
The color rendering index (CRI) of a light source is an objective measure of the ability of the light generated by the source to accurately illuminate a broad range of colors. The color rendering index ranges from essentially zero for monochromatic sources to nearly 100 for incandescent sources. Light generated from a phosphor-based solid state light source may have a relatively low color rendering index.
It is often desirable to provide a lighting source that generates a white light having a high color rendering index, so that objects and/or display screens illuminated by the lighting panel may appear more natural. Accordingly, to improve CRI, red light may be added to the white light, for example, by adding red emitting phosphor and/or red emitting devices to the apparatus. Other lighting sources may include red, green and blue light emitting devices. When red, green and blue light emitting devices are energized simultaneously, the resulting combined light may appear white, or nearly white, depending on the relative intensities of the red, green and blue sources.